1. Field of the Invention
The present invention is related to a fuel feed apparatus that transfers fuel received in a fuel tank having multiple inner tank sections into a sub-tank received in the fuel tank, and supplies the fuel received in the sub-tank to an internal combustion engine.
2. Description of Related Art
A fuel feed apparatus including a fuel pump is provided in a fuel tank having multiple tank sections in a related art (e.g., JP-A-5-2830). In this case, fuel is jetted from the fuel pump into a tank section where the fuel pump is received, so that suction pressure is generated for transferring fuel received in another tank section toward the fuel pump.
Besides, if fuel is decreased in the tank section where the fuel pump is received, the fuel pump cannot draw fuel in the tank section. In this case, fuel in another tank section cannot be drawn by the fuel pump. Accordingly, the fuel pump cannot draw fuel received in the tank section and fuel received in the other tank section.
In another case, a fuel feed apparatus includes a sub-tank receiving a fuel pump in a fuel tank (e.g., U.S. Pat. No. 6,457,945 B2/JP-A-2001-207929). If the fuel tank includes multiple tank sections, and if multiple jet pumps are received in the other tank sections for drawing fuel, fuel received in the other tank sections can be supplied to the sub-tank. Therefore, fuel can be secured in the sub-tank, even when fuel in the sub-tank decreases. However, if the jet pump is installed outside of the sub-tank, fuel is discharged from outside of the sub-tank, and the discharged fuel may not be supplied into the sub-tank when the vehicle is inclined, for example. In this case, fuel received in the sub-tank may decrease.
Fuel returned from a pressure regulator is used in a jet pump in a generally known fuel feed apparatus (e.g., JP-A-2001-20900). In detail, surplus fuel is generated and exhausted from the pressure regulator as return fuel. The return fuel is supplied to the jet pump (drawing pump), so that fuel in the fuel tank is supplied into the sub-tank. The return fuel can be also supplied to a jet pump (transfer pump) used for transferring fuel received in another tank section in the fuel tank into the sub-tank.
However, in this case, when an amount of pressure-controlled fuel discharged from the pressure regulator is increased, an amount of the return fuel exhausted from the pressure regulator decreases. Subsequently, an amount of fuel (return fuel) supplied to both of the jet pumps decreases, and an amount of fuel supplied into the sub-tank by both of the jet pumps decreases. Here, the jet pumps are the drawing pump and the transfer pump. As a result, an amount of fuel received in the sub-tank decreases, and the fuel pump may not properly draw fuel received in the sub-tank.
By contrast, if a consumption amount of fuel drawn from the sub-tank is decreased, the amount of return fuel (i.e., fuel exhausted from the pressure regulator) increases. In this case, the amount of fuel supplied to both of the jet pumps increases, and the amount of fuel supplied into the sub-tank increases. As a result, a large amount of fuel may overflow from the sub-tank, and the overflowing fuel may agitate fuel received in the fuel tank. In this case, vapor of fuel may be generated. Besides, noise may be generated when fuel overflowing from the sub-tank drops onto the inner wall of the fuel tank.
Surplus fuel returning from an internal combustion engine may be supplied to the jet pump, instead of the fuel exhausted from the pressure regulator. However, in this case, an amount of fuel consumed in the engine varies due to a change of an operation condition. In this case, the amount of fuel received in the sub-tank changes.
In a generally known fuel feed apparatus, pressure-controlled fuel is supplied to a jet pump from a pressure regulator having a diaphragm (e.g., U.S. Pat. No. 6,502,558 B1/W099-61777). In this structure, the diaphragm is used for preventing a control characteristic of the pressure regulator from changing due to pressure variation in the downstream side of the pressure regulator. However, if the diaphragm is used in the pressure regulator, the structure of the pressure regulator becomes complicated. Furthermore, the diaphragm needs sufficient surface area for receiving pressure. Accordingly, it becomes difficult to downsize the pressure regulator, if the diaphragm is used in the pressure regulator.